During the initial phases of our Trauma Registry (Project I-A, Offner), we recorded post injury blood transfusion as a surrogate for shock. During routine blood storage, lipids are generated from cellular blood components. To our surprise, in early multi-variant analysis blood transfusion was an independent and robust predictor of acute lung injury (ALI) and multiple organ failure (MOF). Indeed, the risk of ALI/MOF increased with the storage time of the transfused units. Although multiple projects (IA:Offner, II:Biff1, IV:Moore, V:Meng, and VII:Harken) are relating cytokines to ALI/MOF; we are also examining lipids because they increase with storage of packed red blood cells (PRBCs). ALI/MOF require two events: the first involves activation of the vascular endothelium (EC) and priming of the circulating neutrophils (PMNs) resulting in adherence of PMNs with maximal cytotoxic potential (collaboration with Project IV: Moore. These primed, adherent PMNs are "hyperactive" in that agents that normally do not activate quiescent PMNs may activate these primed adherent PMNs. The second event causes activation of these primed PMNs resulting in EC damage capillary leak, and end-organ injury. Our preliminary data has demonstrated prime PMNs, and are etiologic in two event animal models of ALI. Moreover, lipids have also been implicated in human transfusion related acute lung injury. Our global hypothesis is that lipids generated during blood storage are etiologic in post injury ALI/MOF, and removal of these compounds from stored blood will abrogate post injury ALI/MOF. This hypothesis will be tested by completing the following specific aims. Specific Aim 1 will determine if lipids generated during blood storage alter the PMN:EC physiology in vitro. Specific Aim 2 will investigate if washing blood components and/or pre-storage leukodepletion abrogate production of these biologically active lipids in vitro and in an animal model. Specific Aim 3 will change the storage conditions of platelet concentrates to eradicate lipid accumulation. Specific Aim 4 will interrogate the signaling pathways to identify possible therapeutic targets that abrogate PMN-mediated toxicity (with Project IV: Moore and Project VIII:Banerjee). Specific Aim 5 will investigate the effects of washing stored blood components and pre-storage leukoreduction in comparison to stored PRBC transfusion in two separate, prospective clinical trials of patients undergoing orthopedic procedures requiring transfusion: scheduled fracture fixation post injury and elective hip replacement (with Project IA: Offner_. Completion of these specific aims will identify methods to make transfusions safer in critically ill patients .